The invention relates to a camshaft adjuster with a limiting element for limiting the relative motion between two components of the camshaft adjuster. The invention further relates to a method, by which a limiting position of two components can be set, which are moved relative to each other for changing an adjustable angle of a camshaft adjuster.
For modern internal combustion engines, which are used in motor vehicles, the ability to influence the control times, in particular the intake and exhaust times, of the internal combustion engine is desirable. For this purpose, camshaft adjusters are used, which are used for influencing the relative rotational angle position of a camshaft relative to a crankshaft of the internal combustion engine, by which the control times of the internal combustion engine can be influenced depending on operation. This is advantageous, for example, with respect to the shape of the performance pattern, the torque characteristics, the gas emissions values, the consumption, and/or the sound emissions of the internal combustion engine.
For camshaft adjusters, there are different structural forms, for example, camshaft adjusters with integrated gears, for example, a one-stage or multi-stage triple-shaft gear with uniform or non-uniform transmission ratios, a multi-link gear or coupled gear, a wobble-plate gear, an eccentric gear, a planetary gear, a shaft gear, disk cam mechanism, or combinations of the above gear types. A camshaft adjuster with a vane-cell construction or axial-piston construction represents an example, alternative structural form of a camshaft adjuster, in which an adjustment motion is generated by a hydraulic medium. Other possible structural forms are, in particular, those with pivoting vanes or segmented vanes.
All of the above constructions of a camshaft adjuster can be used in the scope of the present invention. An adjustment angle of the camshaft adjuster is here generated by a relative motion of two components of the camshaft moved relative to each other. While such a relative motion can definitely involve a translating or rotational movement, below reference is made, for example, to a rotating relative motion of components constructed as an outer rotor and an inner rotor, as used, in particular, for a camshaft adjuster in vane-cell construction.
One-sided limiting, determining the degree of freedom with or without play for the relative motion can be realized by a limiting element. Here, it can involve, for example, a peg, pin, projection, or the like, which is connected to one component and which is guided in a groove of the other component and which contacts a groove end of the other component for the desired limiting position. Here, a desired pre-setting of the limiting position is problematic due to considerations of the production tolerances for the components, the groove, and the position of the limiting element. To make matters worse, an additional locking element is to be used in the surroundings of the limiting position or in the limiting position itself. This locking element is to stop the camshaft adjuster with or without residual play, for example, by breaking the supply with a hydraulic medium, for example, during the time around the switching off or starting of the internal combustion engine, and/or for locking in an “advanced” or “retarded” operating position of the camshaft adjuster, especially in defined operating situations of the internal combustion engine.
In DE 198 60 418 A1, it became known that limiting the adjustment motion for a camshaft adjuster in vane-cell construction by stopping the vane on the limiting walls of the work chambers oriented in the radial direction is insufficient, especially when a camshaft adjuster with an essentially unchanged structural form is to be used for various internal combustion engines, in which different maximum and minimum adjustment angles and locking positions are desired. Accordingly, it was proposed to provide on one component a stop bolt or an alignment pin, which is fixed or loosely guided in a base borehole by a press fit or by a transition fit. Similarly, it was proposed to form the stop bolt and the base borehole with threading and to screw the stop bolt into the base borehole or also to fuse the stop bolt in the base borehole. In the other component, an angled limiting groove is provided, which can have different sizes for different uses of the camshaft adjuster, in particular, it can extend over different peripheral angles. In addition, a locking pin is provided, which extends through two aligned boreholes of the components, which, when the hydraulic medium pressure is beneath a threshold value is pressurized by a spring into a locking position, while for a hydraulic pressure above the previously mentioned threshold value, the locking pin is pushed out of one component and into the other component. For the case of using both a limiting element in the shape of a stop bolt in an angled limiting groove and also a locking pin, in addition to the previously mentioned tolerances, it also must be taken into account that a locking position lies in an exactly predetermined interval of the region predetermined by the stop bolt and the angled limiting groove. For example, locking must be performed for an end position, that is, for the contact of the stop bolt on the angled limiting groove, so that the end of the angled limiting groove, the position of the stop bolt, and the boreholes, in which the locking pin is guided, must be aligned exactly to each other.
The problems stated above can lead to the result that for a preassembled adjuster, the present sum tolerances must be measured during the assembly of the camshaft adjuster. A matching stop pin is then fitted according to the result. This requires a complicated method during the assembly with high investment, increased requirements on measurement technology and precision, increased tool costs, and assembly line output losses. However, even for such a complicated pairing, the realizable tolerance has a lower limit. Further reduction of the achievable tolerance bands can be achieved only by increasing the expense and possible extraction.